The Zero Carb Diet May Be a Simple Way to Lose Weight—But Is It Safe?

There are digestive side effects, for starters.

Low carb diets have been popular for years. But lately I've been hearing about a zero carb diet, and it has me worried. Depending on what you choose to eat, a no carb diet may be even more restrictive than a keto diet. While there's no precise limit to the grams allowed per day, this approach essentially involves eliminating as much carbohydrate as possible. Considering that vegetables typically contain 3 to 4 grams of net carb (that's grams of total carb minus grams of fiber) per cup, and an ounce of nuts provides about the same, a truly zero carb goal eliminates more health-protective foods than any other diet.

This approach reminds me of the fat free fad I encountered when I first became a dietitian, in that it pushes a trending philosophy to the extreme. Several years ago, when fat was vilified, I saw clients who became obsessed with avoiding fat at all costs. If something contained even half a gram of fat per serving, they would banish it, fearing that those half grams would add up to too many full grams by the end of the day. This mentality led to filling the fat void with carbs and sugar, which ultimately led to weight gain and a host of fat deficiency side effects, from dry skin to hormone imbalances.

As with fat, the focus with carbohydrates should be quality and balance, not banishment. It's absolutely true that there are some bad carbs, such as processed grains and refined sugar; but that's just part of the carb story. Here's an analogy I use with my clients: Some types of workouts can lead to injury. But that being true, it doesn't mean you should avoid working out completely. The goal with exercise is to engage in the right type and amount in order to gain benefits. And the same is true for carbs.

Losing and maintaining a healthy weight and preventing diseases like diabetes doesn't require such extreme carb limits. In fact, the side effects of attempting to eliminate all carbs are very impactful for both quality of life and health. Here are four to consider.

You could miss important nutrients

Slashing carbs severely reduces the intake of many key nutrients found in foods that are shunned or limited, including vitamins, minerals, antioxidants, fiber, and prebiotics (more on this below), and even healthful fats. There is no multivitamin or powdered supplement capable of replacing the myriad health-protective nutrients that stop showing up for work in the body. This shortfall can potentially affect immune function, cognitive health, and up the risk of chronic illnesses, including heart disease and Alzheimer's. In fact, in Blue Zones—areas in the world where people live the longest, healthiest lives—diets are predominantly plant-based and relatively high in carbs.

Carb avoidance could lead to poor digestive health

The daily recommended target for fiber is at least 25 grams per day. And this important nutrient is only found in foods that contain carbohydrates. A high fiber diet is linked to a significantly lower risk of heart disease, stroke, high blood pressure, diabetes, obesity, and some digestive diseases. Certain types of fiber also act as prebiotics, which serve as food for the beneficial gut bacteria that support immunity, anti-inflammation, and mental health. Fiber supplements are available, but research shows that they don't offer the same benefits as fiber derived from whole foods.

You could experience low carb flu

You've probably heard about the keto flu. It happens when someone first adopts a keto diet, with symptoms that may include headaches, brain fog, irritability, dizziness, nausea, and muscle soreness. This occurs as your brain, which typically uses up to 60% of all the carbs you eat, must adapt to a different fuel source. But just because your body can adapt doesn't mean it's ideal. The same is true of renouncing carbs. Again, it's not necessary for weight loss or optimal health, so why put yourself through the torture?

There may be social and psychological side effects

Any extreme diet makes social eating a challenge. I've heard many stories from clients about how their strict diet led to avoiding get togethers with friends and family or caused them to become obsessive or fearful about food. Others who are unable to maintain the restrictions, and thus fall off the wagon, often experience extreme guilt and even depression. Going on and off strict diets is a pattern that can morph into seriously disordered eating and crush people's quality of life and mental health. In addition, a systematic review of 11 studies concluded that plant-based diets that include healthful carbs are associated with significant improvements in emotional well-being, including depression.

Bottom line: a zero carb diet is not necessary or recommended for either long-term weight loss or optimal health. In fact, recent research shows that a plant-based diet that includes whole, fiber-rich foods; monounsaturated fats, like avocado, olive oil and nuts; and plant-based proteins, like lentils and beans, plays a major role in the prevention and management of type 2 diabetes. Plant-based diets, which are moderate to high in carbohydrates, have been shown to generate weight loss, improve insulin resistance, support a healthy gut microbiome, and reduce the formation of advanced glycation end products, or AGEs, compounds associated with aging.

How to include carbs in your diet

Wiping out an entire macro—meaning no carb at all; only fat and protein—may be an easier way to lose weight because it's simple, but it's not better. And for most, it's not sustainable. Instead, up your intake of a wide variety of non-starchy veggies, making them the core of your eating pattern. Include portions of fruit, whole grains, and starchy veggies that are in line with your body's fuel needs, based on your age, gender, ideal weight, and activity level. In other words, a petite, 40-year-old woman with a desk job and 20 pounds to lose shouldn't be eating the same amount of carbs as a tall, 25-year-old, lean male athlete.

Also include anti-inflammatory, satiety-inducing fats that are good for circulation, like avocado and avocado oil; extra virgin olive oil and olives; nuts; seeds; and nut/seed butters. And eat more meatless meals that include lentils, beans, and chickpeas as the protein source. This pattern provides a much broader spectrum of the nutrients needed for wellness, and it's an approach you can stick with long term, which is one of the most important factors for not only shedding pounds but keeping them off for good.

Cynthia Sass, MPH, RD, is Health's contributing nutrition editor, a New York Times best-selling author, and a nutrition consultant for the New York Yankees.

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